Glass keyboard and method for producing a glass keyboard

ABSTRACT

In a glass keyboard comprising a keyboard surface ( 4 ) made from a flexible thin glass pane ( 2 ) and at least one carrier material pane ( 6 ), each pane being provided with an electroconductive layer ( 8,10 ) on the faces facing each other, wherein the opposing electroconductive layers ( 8,10 ) are kept at a distance to each other with the aid of a spacer ( 12 ), and wherein the electroconductive layers ( 8,10 ) touch each other when pressure is applied to the flexible thin glass layer ( 2 ) at the essentially localized place of pressure application, it is provided that the flexible thin glass pane ( 2 ) is made from a drawn thin glass film.

BACKGROUND OF THE INVENTION

The present invention relates to a glass keyboard and to a method forproducing a glass keyboard.

Such pressure switch elements are known as touch panels in displays. Thetouch panels are normally made from transparent plastic films whoseinner surfaces are coated with an electroconductive material. To supportsaid films spacers are glued in the air gap, wherein a spacer arrangedaround the outside of the contact area is bonded in an airtight mannerto the plastic films to stabilize the inside air pressure thussupporting the upper film. Inside the contact area elastic spacers areadditionally provided which ensure return movement of the films. It is adrawback of the known pressure switch element that it requires ahermetically sealed air space which does not allow for any pressurecompensation. In the event of considerable deviation from the normalatmospheric pressure, e. g. during application in submarine vehicles orin aeronautics and space operations, and at high temperatures hairlinecracks occur in the vapour-deposited electroconductive contact layer dueto the changes in air pressure, which results in a failure of the unit.At large heights the spacer in the contact area expands. This changesthe switching path of the contact film, and the given electronical andmechanical parameters, such as the action point, are no longer compliedwith. Further drawbacks of the known touch panels are that the plasticfilms present only a limited mechanical and chemical resistance, a smalldegree of transmission and are not antistatic. Further, in the event oftemperature variation there is the danger of crack formation in theelectroconductive layer due to fact that the expansion coefficients ofthe conductive layer and the plastic carrier considerably differ fromeach other.

From EP 0 546 003 B1 a pressure switch element made from a glasslaminate is known which comprises a flexible thin glass pane and atleast one carrier glass pane, each pane being provided with anelectroconductive layer on the faces facing each other. The opposingelectroconductive layers are kept at a distance to each other with theaid of a spacer. The electroconductive layers touch each other whenpressure is applied to the flexibel thin glass layer at the essentiallylocalized place of pressure load application.

The known pressure switch element comprises a shock andpressure-sensitive thin glass pane.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a glass keyboard withreduced pressure and shock sensititivity thus allowing large-scaleproduction. According to the invention the flexible thin glass pane ispreferably made up of a drawn thin glass film. It is important that thethin glass pane is produced from a drawn thin glass film since only thistype of pane is sufficiently stable and flexible at the same time. Thedrawn thin glass film thus allows production of a break-proof thin glasspane which is flexible enough to allow contact to be established betweenthe electroconductive layers facing each other.

According to an alternative embodiment the carrier material pane isslightly larger than the flexible thin glass pane such that the marginalarea of the carrier material pane protrudes beyond the the marginal areaof the thin glass pane. The protruding marginal area of the carriermaterial pane protects the sensitive marginal edge of the thin glasspane, which can further reduce the danger of breakage of the thin glasspane.

In the marginal area the flat set back margin of the thin glass pane isglued to the marginal area of the carrier material pane by means of anadhesive acting as a spacer. The protruding margin of the carriermaterial pane is further adapted to receive an adhesive build-up whichalso protects the sensivitve edge of the thin glass pane.

Preferably the margin of the thin glass pane is stabilized by means of acured plastic material. The cutting edge of the thin glass pane displaysa plurality of microcracks which occur during the cutting process andextend from the edge to the inside. Said microcracks may easily resultin a crack which destroys the entire thin glass pane. The margin of thethin glass pane is therefore preferably stabilized by means of a curedplastic material. For this purpose the boundary edges of the thin glasspane are dipped into a liquid plastic material. Due to the capillaryeffect the microcracks are filled with the liquid plastic materialwhereafter the plastic material cures. When the plastic material iscured, the thin glass pane offers a considerably higher stability sincebreaking of the thin glass pane starting from its margins can no longeroccur in the event of pressure or shock load.

The keyboard surface made from the flexible thin glass pane may be offlat configuration in the marginal area and present a-slight convexityto the out-side in the keyboard area. The convexity of the keyboardsurface improves on the one hand the return movement behaviour of thethin glass pane after operation and prevents on the other hand theoccurrence of Newton's rings which are undesired in a glass keyboard foroptical reasons.

A thin glass pane is preferably glued to the carrier material pane inthe deep-drawn state of the former. For this purpose the thin glass paneis deep drawn in cold condition and in this condition glued to thecarrier material pane such that the convexity of the keyboard ismaintained.

The thickness of the thin glass pane ranges between approximately 0.1and 0.5 mm, preferably between approximately 0.175 and 0.4 mm. A thinglass pane of such a thickness offers an adequate flexibility to allowfor localized switching contact between opposing electroconductivelayers.

The spacer is arranged exclusively in the marginal area of the keyboardsurface between the thin glass pane and the carrier material pane,wherein in the remaining portion of the keyboard surface switchingoperations can be performed at any location without further spacersbeing provided. The invention preferably makes additional spacers in thearea of the switching section superfluous such that the overall keyboardsurface is available for switching operations without any limitations.

In a preferred embodiment the spacer in the marginal area is made from aplastic material cured under UV-light. This offers the advantage that noseparate spacer has to be provided, and that the spacer can already beformed when the thin glass pane is glued to the carrier material pane.

The carrier material pane is preferably transparent. This allows e. g.keyboard letterings and/or illumination means to be provided behind thecarrier material pane.

Preferably the carrier material pane is made of glass. This offers theadvantage that the expansion coefficients of a carrier material panemade of glass and of the electroconductive layer, e. g. an indium tinoxide layer, display only minor differences such that the danger ofcrack formation in the electro-conductive layer is reduced.

According to a preferred aspect of the invention the carrier materialpane is made from a transparent glass cell with integratedelectroluminescent matrix (EL display glass).

The carrier material pane can be made from multilayer glass to ensureprotection against splintering. Such a glass keyboard can preferably beemployed in areas where there is the danger of explosion or vandalism.The use of multilayer glass further offers the advantage of a cut-offeffect against UV-light.

The carrier material pane may comprise a heating means on the sideaverting the thin glass pane.

The heating means preferably is an electroconductive transparent coatingapplied to the carrier material pane.

The carrier material pane may also comprise an electroconductingshielding layer on the side averting the thin glass pane, said layershielding electromagnetic perturbing radiation occurring behind theglass keyboard, e. g. from the electronic control unit, thus reducingthe susceptibility of the glass keyboard to electromagneticinterference.

The transparent carrier material pane may form an optical filter or beprovided with such a filter.

According to another aspect of the invention the carrier material panecomprises a receiving means for an exchangeable sheet for keyboardlettering on the side averting the thin glass pane. Such a receivingmeans is e. g. configured as an insertion pocket for the exchangeablesheet. The exchangeability of the sheet for keyboard lettering allowsthe functions of certain keyboard fields to be fixed individually or tobe subsequently changed. In the case of machine control it is thuspossible to e. g. assign the keyboard fields on the keyboard surface todifferent functions according to requirement.

The carrier material pane and/or the spacer comprise in the marginalarea vent openings for the space between the thin glass pane and thecarrier material pane. This offers the advantage that pressurecompensation is possible in the event of deviation from the normalatmospheric pressure, e. g. during application in submarine vehicles orin aeronautics and space operations, and at high temperatures such thatthe electroconductive layers on the thin glass pane and the carriermaterial pane are prevented from being damaged.

The vent openings are preferably provided with a filter materialprotecting the glass keyboard from soiling.

The carrier material pane may comprise a light-scattering layer on theside averting the thin glass pane. Such a coating or surface treatmentis advantageous e.g. in the case of background illumination.

The thin glass pane may comprise a decorative margin on its lower side.The decorative margin offers the advantage that on the one hand thekeyboard surface to be operated is limited whereby the switching sectionto be operated is easily recognizable and on the other hand largerproduction and installation tolerances are available for means locatedbehind the pane, such as LCD displays, which may decrease the productioncosts.

Further preferred features of the invention are stated in the subclaims.

Hereunder embodiments of the invention are explained in detail withreference to the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the glass keyboard according to the invention,

FIG. 2 shows a cross-section of the glass keyboard shown in FIG. 1,

FIG. 3 shows an enlarged view of the edges,

FIG. 4 shows a top view of a corner area of the glass keyboard,

FIG. 4A shows the detail of FIG. 4,

FIG. 5 shows a glass keyboard with a multilayer glass pane as carriermaterial pane,

FIG. 6 shows an embodiment with an electroconductive layer on the rearside of the carrier material pane and a decorative margin under the thinglass pane,

FIG. 7 shows a top view of the embodiment shown in FIG. 6, and

FIGS. 8 and 9 show an embodiment of the glass keyboard with an insertionpocket for a sheet behind the carrier material pane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The glass keyboard shown in FIG. 1 comprises a relatively thick lowercarrier material pane 6 and a thin glass pane 2 kept at a paralleldistance to the carrier material pane 6 with the aid of a spacer 12. Thethin glass pane 2 and the carrier material pane 6 are provided withelectroconductive layers 8,10 on the opposing inner faces, theelectroconductive layers 8,10 forming electrodes and establishing aswitching contact when the layers touch each other. For this purpose theflexible thin glass pane 2 may be deformed by essentially localizedpressure application such that an electric contact is establishedbetween the conductive layers 8,10.

Such a configuration of the glass keyboard can be employed for bothanalog glass keyboards where the electroconductive layers 8,10essentially cover the entire keyboard surface 4, and digital glasskeyboards where the electroconductive layers 8,10 are structured andcomprise e. g. a plurality of conductors arranged parallel to eachother. The conductors on the electroconductive layer 8 are preferablyarranged at right angles to the conductors on the electroconductivelayer 10.

The thin glass pane 2 is cut out of a drawn thin glass film and has athickness ranging between approximately 0.1 and 0.5 mm, preferablybetween approximately 0.175 and 0.4 mm. Float glass of the samethickness comprises a tin film which leads to embrittlement of the glassand is thus not suitable for this application. Only thin glass panesproduced from a drawn glass film have an adequate flexibility andbreaking strength which allow even larger keyboard surfaces 4 to beproduced. Further, the glass thickness must be uniform to a high degree.

The thin glass pane 2 has a slight convexity to the outside and is gluedin this condition to the carrier material pane 6 using the spacer 12.For this purpose the thin glass pane 2 is deep drawn with thereremaining a flat marginal area 20. The spacer is preferably formed bythe adhesive glueing the two panes 2,6 together with glueing beingcarried out only at the edge of the marginal area 20 of the thin glasspane 2. The carrier material pane 6 protrudes on all sides beyond thethin glass pane 2 thus allowing for effective protection of thesensitive outer edges of the thin glass pane 2. At the same time theprotruding margin of the carrier material pane 6 forms a supportingsurface for an adhesive build-up 14 which reaches up to the upper edgeof the thin glass pane 2. Said adhesive build-up 14 additionallyprotects the sensitive outer edge of the thin glass pane 2.

The convexity of the thin glass pane 2 to the outside offers theadvantage that higher return movement forces are produced, and that thethin glass pane 2 does not require further spacers to be arranged in thearea of the key-board surface 4. It is important that no spacers areprovided in the switching area 24 of the keyboard surface 4 since itwould not be possible to establish a switching contact in the area ofsuch spacers. The glass keyboard described here can be operated at anylocation of the keyboard surface 4.

Another advantage of the convexity of the thin glass pane 2 to theoutside is that the formation of Newton's rings, which are undesired intransparent keyboards, is prevented.

Employment of glass as keyboard surface 4 offers the advantage that ascratch-resistant glass keyboard with a high degree of transmission iscreated which presents a higher chemical resistance and is antistatic.The thermal expansion coefficients and the deformation behaviours underpressure of glass and electroconductive layer differ from each otheronly to a small degree such that the danger of crack formation in theelectroconductive layers is considerably reduced as compared withplastic films.

The thin glass pane 2 may be edge-stabilized. Edge stabilizing isrealized by dipping the cutting edges of the thin glass pane 2 cut outof a drawn thin glass film into a highly viscous curable plasticmaterial. Due to the capillary effect the liquid plastic materialpenetrates microcracks 18 in the edge area 20 which occur during thecutting process, wherein said microcracks 18 are filled with plasticmaterial 16 by the subsequent curing of the plastic material such thatthere is no longer the danger that the microcracks 18 lead to breaking.This facilitates handling and processing of the thin glass panes 2. Itis however also possible to stabilize the edges only when the thin glasspane 2 is glued to the carrier material pane 6. The adhesive has thenseveral functions, i. e. it acts as a spacer 12 between the thin glasspane 2 and the carrier material pane 6, it acts as edge stabilizer bypenetrating the microcracks 18 in the edge area 20 of the thin glasspane 2, and it acts as outer edge protection for the thin glass pane 2by forming an adhesive build-up 14 on the protruding margin of thecarrier material pane 6. The adhesive build-up 14 is preferably producedin a second working cycle.

The margin of the carrier material pane 6 protrudes beyond the outeredges of the thin glass pane 2 by e. g. approximately 1 mm thus forming,in conjunction with the adhesive build-up 14, an effective protectionagainst shocks on the outer margin of the glass keyboard.

The carrier material pane is preferably made from transparent material.This offers the advantage that the glass keyboard behind the carriermaterial pane can be provided with marking fields or letterings of anyconfiguration. Further, illumination means, e. g. LED lamps forfunctional displays or for illuminating the sheet 48, may be arrangedbehind the carrier material pane 6. Of course, display screens orLCD-displays and similar may also be arranged behind the carriermaterial pane.

A plastic material curing under UV-light is preferably used as adhesive.Such an adhesive offers the advantage that the time of curing can beexactly controlled, which considerably facilitates the productionprocess.

It is particularly advantageous that the carrier material pane 6 is madefrom glass. The thickness of the carrier material pane 6 depends on theanticipated mechanical stresses and amounts preferably to more than 1mm. It is also possible to provide a carrier material pane 6 made ofthin glass if another supporting structure is arranged behind thecarrier material pane 6.

The carrier material pane 6 may also be made from multilayer glass 22.For this purpose the carrier material pane 6 made from glass may beprovided with an adhesive or a film on the side averting the thin glasspane 2 and bonded with a second glass pane. The film may be coloured.Such a multilayer glass serves as protection against splintering and isprovided e. g. when the glass keyboards are employed in areas wherethere is the danger of explosion or vandalism. The use of multilayerglass further offers the advantage of a cut-off effect against UV-light.

The carrier material pane 6 or the multilayer pane 32 may be providedwith an electroconductive layer on the side averting the thin glass pane2, said electroconductive layer serving e. g. as a shielding layer 40against electromagnetic radiation or as a heating means 36.

The electric coating has a resistance value of more than 100 Ω so as toact as sheet heating. At a resistance value of <20 Ω the electriccoating is suited for shielding purposes.

The lower side of the thin glass pane 2 may be provided with adecorative margin 60 in its marginal area 20, the decorative margin 60preferably ending in a dot screen towards the inside. Said decorativemargin is produced by means of the screen printing technique and forms amask defining the switching area 24 of the keyboard surface 4. Thedecorative margin forms a camouflage for the glued marginal area 20,28of the glass keyboard as well as a camouflage for continuous conductorguides for establishing contact between the electroconductive layers8,10. Due to the fact that towards the inside the dot screen of thedecorative margin gradually ends in the transparent area, it is e. g.possible to install an LCD-display behind the carrier material pane witha larger tolerance and thus in a less expensive way.

Further, the decorative margin covers the connecting contacts glued tothe carrier pane.

The carrier material pane 6 may be mat or opaque on the side avertingthe thin glass pane 2 to scatter the light of LED-displays locatedbehind the carrier material pane 6.

In a particularly preferred embodiment a receiving means 44 for anexchangeable insertion sheet 48 is arranged on the side of the carriermaterial pane 6 averting the thin glass pane 2. The insertion sheet 48serves for the marking of keyboard fields of the keyboard surface 4. Theinsertion sheet 48 may e. g. be made of paper on which characters orsymbols may be printed. The paper may be laminated to be water-proof. Ofcourse, the insertion sheet 48 may also be made of plastic material.

In the embodiment shown in FIGS. 8 and 9 the receiving means 44 for theinsertion sheet 48 is made of a transparent or opaque plate 50 which isfastened at a distance to the carrier material pane 6 such that it formsan insertion pocket for the insertion sheet 48.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined the appended claims.

What is claimed is:
 1. A glass keyboard comprising a keyboard surface(4) made from a flexible thin glass pane (2) and having a marginal area(20) and at least one carrier material pane (6), the flexible glass andcarrier material panes (2, 6, respectively) being provided on respectivefaces facing each other with an electroconductive layer (8, 10,respectively), the opposing electroconductive layers (8, 10) being keptat a distance from each other by a spacer (12), the electroconductivelayers (8, 10) touch each other when pressure is applied to the flexiblethin glass pane (2) substantially at a localized area of pressureapplication, the carrier material pane (6) being slightly larger thanthe flexible thin glass pane (2) such that a marginal area (28) of thecarrier material pane (6) protrudes on all sides beyond the marginalarea (20) of the thin glass pane (2), and the marginal area (20) of thethin glass pane (2) is glued to the marginal area (28) of the carriermaterial pane (6) by means of adhesive acting as said spacer (12) formaintaining the electroconductive layers (8, 10) of the respectiveflexible glass and carrier material panes (2,6, respectively) normallyspaced from each other.
 2. Glass keyboard according to claim 1 whereinthe flexible thin glass pane (2) is made from a drawn thin glass film.3. Glass keyboard according to claim 1 wherein the margin area (20) ofthe thin glass pane (2) is stabilized by means of a cured plasticmaterial (16).
 4. Glass keyboard according to claim 1 wherein thekeyboard surface (4) made from the flexible thin glass pane (2) is offlat configuration in the marginal area (20) thereof and includes aslight outward convexity in a switching area (24).
 5. Glass keyboardaccording to claim 1 wherein the thin glass pane (2) forming thekeyboard surface (4) is made from a drawn thin glass film glued to thecarrier material pane (6).
 6. Glass keyboard according to claim 1wherein the thickness of the thin glass pane (2) ranges betweenapproximately 0.1 and approximately 0.5 mm, preferably between 0.175 and0.4 mm.
 7. Glass keyboard according to claim 1 wherein the spacer (12)is arranged exclusively between the marginal areas (20, 28) of the thinglass pane (2) and the carrier material pane (6), and a remainingportion of the keyboard surface (4) is adapted for localized switchingat any location without any further spacer being provided.
 8. Glasskeyboard according to claim 1 wherein the spacer (12) between themarginal areas (20, 28) is made from a plastic material cured underUV-light.
 9. Glass keyboard according to claim 1 vherein the carriermaterial pane (6) is transparent.
 10. Glass keyboard according to claim1 wherein the carrier material pane (6) is made from glass.
 11. Glasskeyboard according to claim 1 wherein the carrier material pane (6) ismade from a transparent glass cell with integrated electroluminescentmatrix.
 12. Glass keyboard according to claim 1 wherein the carriermaterial pane (6) is made from a multilayer glass (32) as protectionagainst splintering.
 13. Glass keyboard according to claim 1 wherein thecarrier material pane (6) comprises a heating means (36) on the sideaverting the thin glass pane (2).
 14. Glass keyboard according to claim13 wherein the heating means (36). is an electroconductive coatingapplied to the carrier material pane (6).
 15. Glass keyboard accordingto claim 1 wherein the carrier material pane (6) comprises anelectroconductive shielding layer (40) on the side averting the thinglass pane (2).
 16. Glass keyboard according to claim 1 wherein thecarrier material pane (6) is transparent and forms an optical filter orcomprises an optical filter.
 17. Glass keyboard according to claim 1wherein the carrier material pane (6) comprises on the side averting thethin glass pane (2) a receiving means (44) for an exchangeable sheet(48) for keyboard lettering.
 18. Glass keyboard according to claim 1wherein at least one of the carrier material pane (6) and the spacer(12) include area vent openings (52) in at least one of the respectivemarginal areas (20, 28) thereof for venting an intermediate area betweenthe thin glass pane (2) and the carrier material pane (6).
 19. Glasskeyboard according to claim 18 wherein the vent openings (52) areprovided with a filter material (56).
 20. Glass keyboard according toclaim 18 wherein the carrier material pane (6) comprises alight-scattering layer on the side averting the thin glass pane (2). 21.Glass keyboard according to claim 18 wherein the thin glass pane (2)comprises a decorative margin (60) on a lower side thereof.
 22. Glasskeyboard according to claim 21 wherein the decorative margin (60) isscreen printing and ends in a dot screen towards an inside.